1. Field of the Invention
The present invention relates to a technology for controlling a space between a head and a recording medium with a capability of controlling levitation amount of the head using electric characteristics between the head and the medium even when the medium is electrically isolated from a ground.
2. Description of the Related Art
In recent years, with an increase in a recording density of a magnetic disk of a magnetic storage device, it is desired to control levitation amount of a head to keep a space between the head and a medium as small as possible. As a control for the levitation amount of the head implemented today, for example, a feed-forward control arranges a heater on the head for heating the head to protrude a magnetic pole section for recording and reproducing data to the medium.
However, in the feed-forward control, when a fluctuation in manufacturing, a change in the atmospheric pressure, or a temperature change occurs, which causes the levitation amount of the head to be dynamically changed, it is likely that the magnetic pole section excessively protrudes, making the head and the medium come into contact with each other.
A system for estimating and controlling the levitation amount of the head using capacitance generated between the head and the medium is disclosed in Japanese Translation of PCT Patent Application No. 2004-518238 and Japanese Patent Application Laid-Open No. H9-91911.
However, in the system disclosed in the conventional technology, it is necessary to ground the medium using some sort of method, making it difficult to practice the system.
This is because, when a medium (such as a magnetic disk) is stored in a magnetic storage device, the medium is electrically isolated from the ground because a bearing, oil, or the like is used to prevent abrasion of a shaft for rotating the medium.
Therefore, even when the medium is electrically isolated from the ground, it is extremely important to control the levitation amount of the head using electric characteristics between the head and the medium.